In recent years, light emitting devices or displays using light emitting elements made of organic materials have been actively developed. Among these, organic electroluminescence (EL) devices, in which a light emitting layer made of an organic thin film, a hole transport layer and an electron transport layer are stacked, are promising displays in terms that they are self-light-emitting devices of carrier injection type and brightness can be obtained as well.
As electron transporting materials or light emitting materials used for these organic EL devices, metal complexes having organic ligands (hereinafter, abbreviated to organometallic complexes) are used and, for example, tris(8-hydroxyquinolinato)aluminum (Alq3), which is an alumiquinolinium complex, can be used in an organic EL element preparation by being vacuum deposited between a hole transport layer and a cathode made of aluminum, and is used as a material having an excellent electron transporting property and a light emitting property.
As film formation methods of the organometallic complexes, a dry process by vacuum deposition is currently the mainstream method, however, a wet process using polymer materials has also been studied from the viewpoint of convenience of preparation process and the fact that can produce a film having a larger area (for example, see Non-Patent Document No. 1).
In addition, various proposals regarding organic-inorganic hybrid materials in which an organic light emitting material is protected by an inorganic oxide such as silica have been made from the viewpoint of stability of organic EL characteristics.
As the organic-inorganic hybrid material, a light emitting hybrid material has been obtained at a relatively low temperature when synthesized by a sol-gel method (for example, see Patent Document No. 1).
In addition, as the organic-inorganic hybrid material, a white light emitting material in which a π-conjugated polymer is homogeneously dispersed in an inorganic matrix, therefore, having excellent weathering resistance has been proposed (For example, see Patent Document No. 2).
By using metal oxides instead of inorganic oxides such as silica, an organic-inorganic hybrid material including an organic ligand which is difficult to prepare using conventional sol-gel methods has also been proposed (For example, see Patent Document No. 3).
On the other hand, when focusing on light emitting inorganic materials, oxides containing rare earth elements are known as fluorescent materials, and preparing an inorganic-organic polymer composite by forming these fluorescent materials as particles and introducing the particulate to organic polymers has been proposed (For example, see Patent Document No. 4).
Also, an organic-inorganic hybrid material in which a light emitting property is applied by introducing rare earth elements into glasses with low-melting points has been proposed (for example, see Patent Document No. 5).
As described above, studies of various light emitting materials regardless of organic materials or inorganic materials have been made, and, in particular, various proposals have also been made since light emitting hybrid materials having both light emission characteristics and weathering resistance due to combination of organic materials and inorganic materials have been studied.